how is pulseaudio supposed to work?

[Will Woods]

On Thu, 2007-12-13 at 20:54 +0200, Pekka Savola wrote:
> Hi,
> 
> Fedora 8 was working fine until I reinstalled it (but keeping my home 
> dir intact).  How sound doesn't work on many applications.  This is 
> likely a pulseaudio issue.
> 
> Having looked at PulseAudio documentation, I haven't found out "the 
> big picture", i.e., how it is supposed to work.  Should there be a 
> daemon running or something?  Lot of docs also say "pulseaudio is now 
> default" but I haven't found out where this can be configured i.e. 
> where you can turn it off again [1] if you don't like it or check that 
> everything is configured as required.

The default setup works like this:

1) /etc/alsa/pulse-default.conf makes pcm.pulse the default ALSA device.
- This file is provided by alsa-plugins-pulseaudio.

2) When you log in through gdm/kdm, HAL grants you read/write access to
the ALSA device nodes.
- This is handled by ConsoleKit, but wdm/xdm don't support it properly.
- Strictly speaking this has nothing to do with PulseAudio.

3) When GNOME/KDE/etc start up, they start pulseaudio.
- Actually, GNOME starts ESD, but /usr/bin/esd -> esdcompat
- esdcompat is provided by pulseaudio-esound-compat
- kde-settings-pulseaudio provides /etc/kde/env/pulseaudio.sh

4) Sound-using apps use ALSA/ESD as usual.
- It's all actually going through pulseaudio, though.

So - if you're not using GNOME or KDE, or if you're logging in through
xdm or wdm, or if you're missing some packages, audio might not work
right.

If you upgraded your system, the easiest thing to do is:
# sudo yum groupupdate sound-and-video gnome-desktop kde-desktop
(you can remove GNOME or KDE at your discretion)

Oh, and if something else has already claimed the ALSA device,
pulseaudio won't start properly. So you will want to make sure you get
the packages set up right and *then* log out and back in, or reboot.

If you really *must* disable PulseAudio, removing or renaming
/etc/alsa/pulse-default.conf is the easiest way.

Hope that helps,

-w
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